This application claims priority under 35 U.S.C. §119(a) on Patent Application Number 2005-192412, filed in Japan on Jun. 30, 2005, the entire contents of which are hereby incorporated by reference.
The present invention relates to an optical head having a construction for performing optical-axis adjustment of laser light, and to an optical pickup device employing such an optical head.
An optical pickup device lets laser light emitted from a laser diode pass through a collimator lens, a beam-shaping prism, an objective lens and the like to irradiate an information storage medium, and by a light detector reads light reflected from the surface of the information storage medium as an optical signal.
The laser light is parallelized by the collimator lens, shaped into a circular beam by the beam-shaping prism, passes a beam splitter to be focused by the objective lens, and is irradiated onto the information storage medium. The light reflected from the information storage medium is guided by the objective lens to be reflected in rectangular direction by the beam splitter, and received by the light detector. In order for the laser light to pass through a prescribed optical path like this, each optical component is positioned such that optical axes coincide.
While the laser diode emitting the laser light is positioned for the optical axis of the laser light to coincide with the optical axis of the optical pickup device, the laser diode shows variances in the optical axis depending on individual manufactured products. Therefore, for each individual manufactured product the installation angle and position of the laser diode need to be adjusted.
For this reason, optical heads in which a laser diode is fixed are provided with a construction for adjusting the optical axis of the laser light.
Constructions relating to optical-axis adjustment of optical heads in conventional optical pickup devices will be described based on FIG. 9 through FIG. 11.
FIG. 9 is an outline view of an optical head of a first conventional example. FIG. 10 is an outline view of an optical head of a second conventional example. FIG. 11 is an outline view of an optical head of a third conventional example.
For example, the optical head 101 of the first conventional example includes a laser diode 111, a holder 121 retaining the laser diode 111, and an adapter 131 fixing the holder 121 to a housing 141, the holder 121 being fixed to the adapter 131 by holder fixation screws 171, and the adapter 131 being fixed to the housing 141 by adapter fixation screws 181. The construction involves screwing the holder fixation screws 171 out and in for tilting the holder 121 to adjust the tilt of the laser diode 111, as well as adjusting the adapter fixation screws 181 for moving the adapter 131 with the holder 121 as a whole to adjust the position of the laser diode 111 (see JP H2-294949A).
Also, the optical head 201 of the second conventional example includes a laser diode 211, an adjustment strip 221, which adjusts the tilt of the laser diode 211, and a fixation board 291, which fixes the laser diode 211 against the adjustment strip 221. The adjustment strip 221 is a U-shape made from a flat strip, one of the even sections being fixed to a housing 231, with an opening 223 provided approximately in the center portion of both even sections, into which the laser diode 211 is fixedly inserted. The U-shaped adjustment strip 221 is provided with an adjustment screw 271 at its end. By screwing this adjustment screw 271 out and in, the gap of the U is widened and narrowed to adjust the degree of parallelity of the U, by means of which the tilt of the laser diode 211 is enabled to be adjusted. Also, because the diameter of the opening 223 is somewhat greater than the diameter of the laser diode 211, the position of the laser diode 211 is enabled to be adjusted (see Japanese patent publication 2835778).
Also, the optical head 301 of the third conventional example includes a laser diode 311, a retaining holder 381 that retains the laser diode 311, and a fixation seat 321 that retains the retaining holder 381. The retaining holder 381 is provided in its center portion with an opening 383 for fixing the laser diode 311. The laser diode 311 is fixed, its outer edge having been shaped into a spherical surface portion 385 by spherical machining. On the other hand, the fixation seat 321, which retains the retaining holder 381, is provided in its center portion with a fixation-seat opening 323. This fixation-seat opening 323 is provided with a spherical receiving portion 325, which has been machined into a spherical surface that abuts the spherical surface portion 385 of the retaining holder 381. Consequently, the spherical surface portion 385 and the spherical receiving portion 325 move rotationally while making sliding contact, thus enabling the tilt of the optical head 301 to be adjusted. Also, because the emission point of the laser diode 311 is positioned such as to come to lie in the center of the spherical surface, the location of the emission point does not change even when changing the tilt. (JP H5-81693A).
However, in each of the conventional examples the optical-axis adjustment is a difficult operation, requiring time at the time of adjustment.
Specifically, in case of optical-axis adjustment by the first conventional example, it would be necessary to screw out and in each of the screws 171, 181, which would require time. Also, although by screwing out and in the holder fixation screws 171 to tilt the holder 121 the laser diode 111 is tilted, the location of the emission point of the laser diode 111 is unintentionally changed at the time. That is, because the holder 121 is tilted with fixation screws on one side of holder 121 acting as fulcrum, the emission point of the laser diode 111 fixed to the holder 121 moves around a center at the fulcrum. Therefore, even if one desired to adjust the tilt of the laser light only, it would be necessary to perform locational adjustment as well.
Also, in case of adjusting the tilt of the laser diode 211 in the second conventional example, although there being the merit of being able to adjust using a single adjustment screw 271, the adjustment strip 221 is tilted pivoting on the end portion opposite from where the adjustment screw is located. Therefore, there would be the problem that the location of the emission point of the laser diode 211 fixed to the adjustment strip 221 changes. Also, in case of carrying out locational adjustment, loosening and fastening the screws of the fixation board 291 would still be required and consume time.
Furthermore, in the third conventional example, although the location of the emission point of the laser diode 311 does not change, in case of carrying out locational adjustment of the laser diode 311 it would be necessary and time-consuming to loosen the bond of the fixed seat 321 with the housing in which it is fixed, to carry out the locational adjustment.